These additives are conventionally prepared in two steps. The first step comprises the phosphorylation of the alcohol with phosphorous sulphide and the second step comprises the treatment of the phosphorylated product with a metal oxide, hydroxide and/or salt.
The first step of this process is slow. In order to obtain commercially feasible reaction rates it may be necessary to heat the reaction mixture to such temperatures that decomposition of the phosphorylation product may occur. In particular in the case of the phosphorylation of phenol or substituted phenols this step is very slow, and on heating, decomposition of the phosphorylated product is likely to occur.